Base for office chairs



1.1 is a top perspective view of a base for office chairs, showing my new design;

1.2 is another top perspective view thereof, from a different angle than view 1.1;

1.3 is a bottom perspective view thereof;

1.4 is a front view thereof;

1.5 is a rear view thereof;

1.6 is a left view thereof;

1.7 is a right view thereof;

1.8 is a top view thereof;

1.9 is a bottom view thereof; and

1.10 is a cross-sectional view thereof, taken along line A-A of the view 1.8. 

CLAIM The ornamental design for a base for office chairs, as shown and described. 